US Patent 7299941 Container seal with flexible central panel

A seal mountable to the rim of an open mouth container the seal including a resiliently flexible central panel separately formed from and intimately bonded to a substantially rigid peripheral mounting ring adapted to snap-mount to the rim of the container with the central panel being selectively flexible both inward and outward relative to the interior of the container for the accommodation of both overfilled and underfilled conditions through a variation in the head space beneath the mounted seal.